Emergency locking gas spring

ABSTRACT

An adjustable installation includes a body and a member carried by the body for adjustment among a plurality of positions by movements substantially in tandem of two spaced-apart locations on the member. A controllable locking gas spring is coupled between the body and the member at one of the locations, and an emergency locking gas spring is coupled between the body and the member at the other of the locations. The emergency locking gas spring normally acts like a non-locking gas spring and is thus in a follower relationship to the controllable locking gas spring but is locked automatically in either of two ways, depending on its design. In some designs, the emergency locking gas spring locks when a force greater than a predetermined force is imposed on it. In other designs, the emergency locking gas spring is locked in response to a signal generated by an acceleration detector upon detection of an acceleration of the installation greater than a predetermined acceleration.

BACKGROUND OF THE INVENTION

Locking gas springs are well known and widely used in applications inwhich a member is moved by a spring force to a selected position andlocked in that position. Perhaps the most well-known and common use oflocking gas springs is in the seat support columns of office chairs.When most or all of the user's weight is off the seat and a controllever is moved to a release position, the spring force extends thespring and raises the seat. When the user sits on the seat and the gasspring is released, the user's weight overcomes the gas spring force,thus compressing the spring and lowering the seat. The user can adjustthe seat to any desired height and by releasing the control lever whenthe desired height has been attained lock the seat in the desiredposition. Locking gas springs can be used for other adjustableinstallations, such as hospital beds, various forms of work tables andstands, and adjustable vehicle seat backs, such as for motor vehiclesand aircraft.

Safety standards for the seat backs of motor vehicles and aircraft arereadily met by locking gas springs used in tandem, that is, a lockinggas spring on each side of the seat back. The necessity for tandeminstallations arises from the need to carry the very high forces imposedon the seat back in a crash, such as the rearward forces that occur whena motor vehicle is rear-ended and the seat occupant is forced backagainst the seat back by inertial forces or during the rebound phase ofa front end collision when the occupant is forced back against the seatback by a restraint system. The tandem use of locking gas springs invehicle applications requires synchronous control of the two springs bymeans of relatively costly control linkages.

SUMMARY OF THE INVENTION

One object of the present invention is to provide an adjustableinstallation, such as a vehicle seat back, that uses gas springs intandem but does not require linking them, thus eliminating costly andcomplicated components. Another object is to provide an installation,especially for use in vehicles, in which two gas springs are locked andthus able to sustain the high forces that may be imposed on them in acrash. Yet a further object is to provide a gas spring that normallyfunctions as a non-locking gas spring but that locks when a high forceis imposed on it or is caused to lock by the sensing of a highacceleration of the installation in which it is used.

The foregoing objects are attained, in accordance with one aspect of thepresent invention, by an adjustable installation comprising a body and amember carried by the body for adjustment among a plurality of positionsby movements substantially in tandem of two spaced-apart locations onthe member. A controllable locking gas spring is coupled between thebody and the member at one of the locations, and an emergency lockinggas spring is coupled between the body and the member at the other ofthe locations. The emergency locking gas spring normally acts like anon-locking gas spring and is thus in a follower relationship to thecontrollable locking gas spring but is locked automatically in either oftwo ways, depending on its design. The term "follower relationship" isused herein to mean that the emergency locking gas spring (1) extendsand exerts a spring force when the controllable locking gas spring isreleased and extends and (2) is compressed when the controllable gasspring is released and is compressed by an external force applied to theinstallation. In some designs of the emergency locking gas spring, theemergency locking gas spring locks when a force greater than apredetermined force is imposed on it. In other designs, the emergencylocking gas spring is locked in response to a signal generated by anacceleration detector upon detection of an acceleration of theinstallation greater than a predetermined acceleration.

An emergency locking gas spring for an installation according to thepresent invention will include a cylinder, a body of liquid in thecylinder, a rod piston movably received in the cylinder in sealedrelation and having a bypass through which the liquid flows uponmovement of the piston, and a system for preventing liquid from flowingthrough the bypass in the event of an emergency that could cause themovable member to move under a high force against the restraint of theemergency locking gas spring. Suitable systems for closing the bypass inan emergency include: a valve that is normally open to allow liquid flowthrough the bypass but closes when a force in excess of a predeterminedforce is applied to the rod piston; a quantity of an electro-rheologicalliquid contained in the cylinder and a detector and energizationinstallation responsive to an acceleration of the installation in excessof a predetermined acceleration for energizing the liquid to increaseits viscosity such as to substantially prevent the liquid from flowingthrough the bypass; a quantity of a magneto-rheological liquid containedin the cylinder and a detector and energization system for sensingacceleration of the installation in excess of a predeterminedacceleration and imposing a magnetic field on the liquid to increase itsviscosity such as to substantially prevent the liquid from flowingthrough the bypass.

In some embodiments of systems using a valve to close the bypass, thevalve is a member that normally is in clearance from a port of thebypass to allow liquid flow through the bypass when the piston movesunder a force less than a predetermined force but is movable intosealing relation to the port by a force due to hydrodynamic pressureimposed on the valve member when the force on the piston exceeds thepredetermined force. Such a valve member may be of elastomeric materialand is shaped and dimensioned to deform and close the bypass under ahigh hydrodynamic pressure. With such a valve, a high force imposed onthe piston in an emergency produces a high acceleration of the piston,thus producing a high hydrodynamic pressure that acts on the valvemember such as to close it.

Another suitable valve member is a member of an elastomeric materialhaving walls defining a passage that forms at least a portion of thebypass, the walls and passage being shaped and dimensioned such that thewalls collapse and close the passage in response to liquid flow throughthe passage at a velocity in excess of a predetermined velocity. Inparticular, the walls may define a passage having a variablecross-sectional area, the area increasing in the direction of the liquidflow to which the valve responds by closing. In such a design, theincrease in the area in the direction of flow produces a zone of reducedpressure within the passage which, along with the high pressure outsidethe walls of the passage, causes the walls to collapse and close thepassage.

In preferred embodiments, the emergency locking gas spring includes acylinder having a closed end and an open end, a piston rod having aportion received in the cylinder and a portion extending out of thecylinder through the open end, and a seal package received in the openend of the cylinder in sliding and sealed relation to the piston rod andsealed and fixed relation to the cylinder and defining within the pistonmember a closed chamber. A rod piston is affixed to the portion of thepiston rod within the chamber and has a piston seal in sliding andsealed relation to the cylinder and defining in the chamber a closed endsection and an open end section, each of a volume that varies inaccordance with the position of the rod piston axially of the cylinder.A floating piston received in the open end section in sliding and sealedrelation to the cylinder and the piston rod defines in the open endsection a gas part between the seal package and the floating piston anda liquid part between the floating piston and the rod piston. A body ofliquid, such as oil, is contained in the closed end section and theliquid part of the open end section. A body of gas under pressuresubstantially above atmospheric pressure is contained in the gas part ofthe open end section. A bypass in the rod piston allows the liquid toflow through the bypass upon movement of the rod piston except when avalve closes the bypass upon an acceleration of the piston in excess ofa predetermined acceleration.

The present invention is especially useful for adjusting the backs ofvehicle seats. The controllable locking gas spring and the emergencylocking gas spring act in tandem by applying forces to both mountinglocations (both sides of the seat back) to move the seat back to itsupright-most position when the controllable locking gas spring isreleased and the user leans forward. With the controllable locking gasspring released, the user can lean back against the seat back to apply aforce against the biases of the gas springs and tilt the seat back to adesired tilted-back position. When the seat back is in the desiredposition, the user locks the controllable lock spring. Under normalconditions, the controllable locking gas spring holds the seat back inthe adjusted position. Although the emergency locking gas spring appliesa bias to the seat back toward the upright position, it is not lockedand is essentially in a follower relationship to the controllablelocking gas spring.

In an emergency, the emergency locking gas spring locks and is capableof enduring a very large force and preventing the seat back from movingagainst the locking direction. As described in more detail below, bothgas springs are locked primarily in one direction and can yield in theother direction. In a seat back adjusting installation, the seat back islocked against tilting rearwardly. While the seat back may move forwardto its full upright position against the biases of both gas springs, thelinkage between the frames of the seat bottom and seat back may be madesufficiently strong to sustain high forces in a crash.

The installation is cost efficient, in that it does not require alinkage such as the one needed for coupling two controllable locking gassprings to control them in tandem. The costs of producing and installingan emergency locking gas spring are comparable to those of producing andinstalling a controllable locking gas spring.

For a better understanding of the invention, reference may be made tothe following description of exemplary embodiments, taken in conjunctionwith the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic three-quarter pictorial view of a vehicle seatinstallation;

FIG. 2 is a schematic axial cross-sectional view of an emergency lockinggas spring suitable for an installation, such as the one shown in FIG.1;

FIG. 3 is a detail axial cross-sectional view of the rod piston of thegas spring of FIG. 2, as indicated by the circle 3, 4 of FIG. 2, showingthe piston on a larger scale than in FIG. 2 and showing the bypass inits open condition;

FIG. 4 is another detail axial cross-sectional view of the rod piston ofthe gas spring of FIG. 2, showing the piston on a larger scale than inFIG. 3 and showing the bypass in its closed condition;

FIG. 5 is an axial cross-sectional view of another rod piston that canbe provided in the gas spring of FIG. 2;

FIG. 6 is a schematic axial cross-sectional view of an other form ofemergency locking gas spring suitable for an installation, such as theone shown in FIG. 1; and

FIG. 7 is a detail axial cross-sectional view of the rod piston of thegas spring of FIG. 6, as indicated by the circle 7 of FIG. 6, showingthe piston on a larger scale than in FIG. 6.

DESCRIPTION OF THE EMBODIMENTS

In FIG. 1 the reference numeral 10 indicates the frame of a vehicle seatof the type having an adjustable back. The frame 10 includes a seatbottom frame 12 having side members 12a and 12b and a seat back frame 14having side members 14a and 14b. The rearward ends of the respectiveside members of the seat bottom frame support the lower ends of the sidemembers of the seat back frame for pivotal movement at two spaced-apartlocations, namely, pivot couplings 16a and 16b at the lower back of eachside of the seat. The pivot couplings allow the seat back to be adjustedto any position between an upright position (as shown) and a rearwardlytilted position (not shown).

The lower end of the side member 14a of the seat back frame 14 extendsdownwardly below the pivot coupling 16a and is connected by a pivotcoupling 18a to a fitting 20 on the cylinder 21 of a controllablelocking gas spring 22, which may be of any suitable construction, suchas a Stabilus "BLOC-O-LIFT" gas spring made by Fichtel and Sachsindustries, Inc., of Colmar, Pa. The piston rod 24 of the gas spring 22is connected by a fitting 26 to a pivot coupling 28a on the seat bottomframe member 12a. Upon movement of an adjustment lever 30 to a releaseposition, the gas spring 22 exerts a compression force between the pivotcouplings 18a and 28a that biases the seat back 14 toward its uprightposition. If the user leans forward, the seat back will be pushed by thegas spring 22 to the upright position. By pushing back against the seat,the user can tilt the seat back against the bias of the gas spring 22 toa desired position. Upon release of the adjustment lever 30, the gasspring 22 locks and holds the position of the seat back.

An emergency locking gas spring 40 is coupled by a pivot coupling 18b,which is located below the coupling 16b, and a fitting 42 on thecylinder 44 to the lower end of the seat back frame member 14b and by apivot coupling 28b and a fitting 45 on the piston rod 46 to the seatbottom frame member 12b. The emergency locking gas spring 40 normallyexerts a force between the seat bottom frame and the seat back framethat biases the seat back to an upright position but yields to arearward force exerted by the user on the seat back to enable the seatback to be tilted rearwardly against the bias when the controllablelocking gas spring 22 is released. In normal operation of the two gassprings 22 and 40, the controllable locking gas spring 22 holds the seatback in the desired position, and the emergency locking gas spring 40 isin a follower relationship to the controlled locking gas spring.Depending upon its design, the emergency locking gas spring 40 locks inresponse to either (1) a force imposed on it in excess of apredetermined force or (2) a signal generated by an accelerationdetector that detects an acceleration of the vehicle greater than apredetermined acceleration.

One embodiment of an emergency locking gas spring 40 suitable for thevehicle seat of FIG. 1, as shown in FIGS. 2 to 4, includes the cylinder44 and piston rod 46 (referred to above). The cylinder has a closed end44ce and an open end 44oe. The piston rod 46 has a portion 46i receivedin the cylinder and a portion 46o extending out of the cylinder throughthe open end 44oe. A seal package 48 received in the open end of thecylinder is in sliding and sealed relation to the piston rod 46 andsealed and fixed relation to the cylinder 44 and defines within thecylinder a closed chamber 50.

A rod piston 52 affixed to the portion 46i of the piston rod within thechamber 50 carries a piston seal 54 that is in sliding and sealedrelation to the cylinder and defines in the chamber 50 a closed endsection 50c between the piston seal and the closed end of the cylinderand an open end section 50o between the piston seal 54 and the sealpackage 48, each section having a volume that varies in accordance withthe position of the rod piston 52 axially of the cylinder 44.

A floating piston 56 and an associated back-up washer 57 received in theopen end section 50o in sliding and sealed relation to the cylinder 44and to the piston rod 46 define in the open end section 50o (1) a gaspart 50og between the seal package 48 and the floating piston 56, whichcontains a gas at a pressure considerably above atmospheric pressure,and (2) a liquid part 50ol between the floating piston 56 and the rodpiston seal 54, which contains a liquid, such as oil. The closed endsection 50c also contains the liquid. The gas in the gas part 50ogmaintains the liquid in the chamber under high pressure at all times,thereby providing the spring force, which is a force due to the gas (andliquid) pressure (gauge) acting over the area of the piston rod 46within the seal of the seal package 48.

The rod piston 52 has a disc-like base plate 52p that is fastened to thepiston rod 46. Holes on the base plate accept studs 52s on a rod pistonbody 52b, the studs being peened over to provide retaining heads thatsecure the body 52b to the base plate 52p. A central cavity 52c in therod piston body receives an insert 58, which has a hole 60, a recess 61and radial slots 58s that form parts of a bypass through which liquidcan flow in either direction between the liquid part 50ol of the openend section 50o of the cylinder chamber and the closed end section 50c.Radial slots 63 in the piston body communicate with the slots 58s in theinsert.

A shuttle valve member 66 of an elastically deformable material is heldin a clearance relation to the walls of the cavity 52c by L-shaped ribs52r and in clearance relation to the insert 58 by several bosses 58b onthe insert located in spaced-apart relation concentrically to the hole60, thus providing for flow of liquid around the perimeter of theshuttle valve member to and from the bypass hole 60. The rod piston body52b has a central hole 52h in a transverse end wall 52w of the cavity52c that also forms part of the bypass.

In the state of the rod piston assembly shown in FIG. 3, liquid can flowin either direction through the rod piston bypass (the hole 52h, theclearance around the perimeter of the shuttle valve member 66, the hole60, the recess 61, and the radial slots 58s and 63) as the piston rodextends from or retracts into the cylinder chamber 50 during adjustmentsof the seat back or other member with which the gas spring is used. Inthat regard, the "BLOC-O-LIFT" gas spring 22 and similar controllablelocking gas springs have bypasses that limit the speed of extension andretraction. Accordingly, even if the user should exert a large forcerearwardly on the seat back during adjustment, the piston rod of theemergency locking gas spring 40 of FIGS. 2 to 4, as it is compressed infollowing relation to the gas spring 22, moves sufficiently slowly toprevent liquid flowing through the bypass from attaining a hydrodynamicpressure large enough to deform the valve member 66 and close thebypass.

In a crash of a vehicle having a seat back 14 supported by the emergencylocking gas spring 40 (see FIG. 1), it is possible that the seat backwill be subjected to a force acting to tilt the seat back rearwardlythat is sufficiently high to move the piston rod and rod piston rapidlytoward the closed end of the cylinder (down in FIGS. 2 to 4). Asdiscussed above, the controllable locking retractor is locked againstretraction, but a high force on the seat back can deform the seat backitself, moving the side supported by the emergency locking gas springrearwardly. A high force imposed on the rod piston and resulting inrapid acceleration of the rod piston toward the closed end produces ahigh velocity jetting of liquid through the hole 52h in the rod pistonbody 52b, which acts against the center region of the deformable shuttlevalve member 66 and deforms the valve member in a cup-like fashion sothat it engages the wall of the insert 58 around the hole 60 andprevents liquid from flowing through the rod piston bypass from theclosed end section 50c into the liquid part 50ol (see FIG. 4). Liquid istrapped in the closed end section and prevents the rod piston 52 frommoving toward the closed end of the cylinder, even against forces ofseveral hundred pounds.

High forces acting on the seat back 14 and tending to move it to anupright position can overcome the resisting forces of the gas springs 22and 40 by compressing the gases contained in the open end gas-containingparts of the cylinder chambers. Therefore, the seat back should beconstructed with mechanical stops to limit forward tilting of the seatbeyond its normal upright position. Alternatively or in addition, thegas springs can be designed with mechanical stops to limit the extensionof the piston rods beyond that required to attain the upright-mostposition of the seat back.

Various forms of valves that allow liquid to flow through the rod pistonbypass in normal conditions but close upon rapid acceleration of the rodpiston toward the closed end of the cylinder are possible. One exampleof another form of valve is shown in FIG. 5. The components of the rodpiston of FIG. 5 are substantially the same as the rod piston of FIGS. 2to 4 and are, therefore, designated by the reference numerals used inFIGS. 2 to 4 increased by 100.

A valve member 166 of an elastomeric material has an annular bodyportion 166b that is received in captured and sealed relation within thecavity 152c of the piston body 152b between an insert 158 and atransverse end wall 152w. A nozzle-like tubular portion 166t extendsfrom the body portion freely through a hole 152h in the wall 152w. Apassage 166p that is narrowest at the free end 166e of the tubularportion and progressively widens toward a port 166p' in the body portion166b allows liquid to pass in either direction through the rod pistonbypass (hole 160, recess 161, and slots 158s and 163) under normalconditions, i.e., when the emergency locking gas spring is beingextended or compressed in follower relationship to the controllablelocking gas spring during adjustment of the seat back.

In an emergency, such as a crash of the vehicle, that causes a highforce to be imposed rearwardly on the seat back 14, the piston 152 isaccelerated rapidly toward the closed end of the cylinder (down in FIG.5). Liquid in the closed end section (50, FIG. 2) begins to flowvirtually instantaneously at a high hydrodynamic pressure through thenarrow end of the tube portion 166t of the valve member 166. Theprogressive enlargement of the passage produces a low pressure zonealong the walls of the passage downstream from the narrow inlet end.Meanwhile, the outer walls of the tube portion 166t are subject to ahigh hydrodynamic pressure, resulting from acceleration of the rodpiston 152 against the liquid. The pressure difference between theinside and outside walls of the tube portion 166t cause it to constrictand close the passage 166p. Closing of the passage 166p stops the flowof liquid through the rod piston bypass, and the trapping of liquid inthe closed end section 50c (FIG. 2) of the chamber 50 of the gas springprevents the rod piston from moving farther toward the closed end 44ceof the cylinder. The emergency locking gas spring cannot be compressed,and the side of the seat back 14 (FIG. 1) supported by the emergencylocking gas spring is prevented from tilting back.

Another embodiment of an emergency locking gas spring 240 suitable foruse on one side of an installation in which a member is supportedrelative to a body at two locations by gas springs is shown in FIGS. 6and 7, in which corresponding components are given the referencenumerals of FIG. 2 increased by 200. The liquid contained in the closedend section 250c and the liquid part 250ol of the open end section ofthe gas spring chamber 250 is a magneto-rheological liquid. The rodpiston 252 has a bypass 252h through which the liquid can normally flowas the rod piston 252 moves in either direction along the cylinder whenthe position of the member supported by the gas spring 240 is beingchanged.

A power supply 268 is connected by a wire 270 that runs through thepiston rod 246 from a terminal 272 to one end of an electromagnetic coil276 that is installed in an annular compartment of the rod piston 252surrounding the bypass 252h. The other end of the coil 276 is connectedto ground G by sliding spring contacts 278 that engage the walls of thecylinder 244. The supply of current to the coil 276 is controlled by anacceleration detector 280. In a vehicle, the acceleration detector mayalso be associated with one or more components of an occupant restraintsystem. Upon sensing an acceleration of the vehicle (or other memberwith which the gas spring 240 is used) greater than a predeterminedacceleration, current is conducted through the coil, thus producing amagnetic field in the bypass 252h. As is known per se, the viscosity ofthe magneto-rheological liquid in the bypass 252h is increased by themagnetic field sufficiently so that the liquid is unable to flow throughthe bypass 252h. The liquid trapped in the closed end section 250c ofthe chamber (between the rod piston 252 and the closed end 244ce of thecylinder 244) prevents the rod piston 252 from moving toward the closedend 244ce of the cylinder, thus keeping the emergency locking gas spring240 from compressing under the emergency load.

An emergency locking gas spring substantially identical to the one shownin FIGS. 6 and 7 can be provided with electrodes on opposite sides ofthe bypass 252h instead of a coil around the bypass and contain anelectro-rheological liquid. Upon energization of the electrodes, theelectric field across the passage increases the viscosity of the liquidin the bypass and stops liquid flow through the bypass.

I claim:
 1. An emergency locking gas spring comprisinga cylinder havinga closed end and an open end, a piston rod having a portion received inthe cylinder and a portion extending out of the cylinder through theopen end, a seal package received in the open end of the cylinder insliding and sealed relation to the piston rod and in seated and fixedrelation to the cylinder and defining within the cylinder a closedchamber, a rod piston affixed to the portion of the piston rod withinthe chamber and having a piston seal in sliding and sealed relation tothe cylinder and defining in the chamber a closed end section betweenthe piston seal and the closed end of the cylinder and an open endsection between the piston seal and the sell package, each sectionhaving a volume that varies in accordance with the position of the rodpiston axially of the cylinder, a floating piston received in the openend section in sliding and sealed relation to the cylinder and thepiston rod and defining in the open end section a gas part between theseal package and the floating piston and a liquid part between thefloating piston and the rod piston, a body of liquid contained in theclosed end section and the liquid part of the open end section, a bodyof gas under pressure substantially above atmospheric pressure containedin the open end section and pressurizing the liquid part of the closedend section, a bypass in the piston through which the liquid flows uponmovement of the rod piston, and valve means for closing the bypass inresponse to an acceleration of the rod piston greater than apredetermined acceleration, the valve means including a valve memberthat normally is in clearance from a port of the bypass and is movableinto sealing engagement with the surface around the port by a force dueto a hydrodynamic pressure imposed on the valve member, the valve membercomprising a body of elastomeric material having a portion that normallyoverlies the port of the bypass with a clearance to allow liquid to flowthrough the bypass and that is deformable by liquid pressure into sealedrelation with the port of the bypass to prevent liquid from flowingthrough the bypass.
 2. An emergency locking gas spring according toclaim 1 wherein the port opens at a surface of the rod piston facing theclosed end section.
 3. An emergency locking gas spring according toclaim 1 wherein the body is received in a valve chamber of the rodpiston, the valve chamber being defined in part by a wall on a side ofthe piston opposite the surface, and the wall having a hole generallyaligned axially with the port that directs liquid against a portion ofthe body opposite the port.